Electrostatic precipitator



May 10, 1966 W. VAN LUIK, JR., ET AL. 3,250,060

Inventors..- Prank W VanLU/,Jn, Norman H. Wood, *Edward /L/Szona The/rAttorney May 10, 1966 F, W. VAN LUIK, JR., ET A1. 3,250,060

ELECTROSTATIC PRECIPITATOR 8 Sheets-Sheet 2 Filed Aug. 28, 1963 May 10,1966 F. w. VAN LUIK, JR., ETAL 3,250,060

ELECTROSTATIC PRECIPITATOR 8 Sheets-Sheet 3 Filed Aug. 28, 1965Inventors Frank W Var/Lu ik, Jr, Norman H. Wooo Edward G. Krc/szona. bym .www

The/r A tto/"nay May 10, 1966 F. w. VAN LUIK, JR., ET Al. 3,250,060

ELECTROSTATIC PRECIPITATOR Filed Aug. 28, 1963 8 Sheets-Sheet 4 Y"Inventors: w v Frank W l/anLU/Jm Norman H. Wood, Edward G. /ruszona,

The/'r A ttor/wey pige.

May 10, 1966 F. w. VAN LUIK, JR., ET AL 3,250,060

ELECTROSTATIC PRECIPITATOR 8 Sheets-Sheet 5 Filed Aug. 28, 1953 f milfNAH May 10, 1966 F. w. VAN LUIK, JR., ET A1. 3,250,060

ELECTROSTATIC PRECIPITATOR 8 Sheets-Sheet Filed Aug. 28. 1963 May 10,1966 F. w. VAN Lu1K,JR., ET AL 3,250,060

ELECTROSTATIG PRECIPITATOR 8 Sheets-Sheet '7 Filed Aug. 28, 1963 J ,a y@Mmm m wwo ,MWMHKHA WWadM im? m P E M.

F. W. VAN LUIK, JR., ET AL.

ELECTROSTATIC PRECIPITATOR Filed Aug. 28, 1963 8 Sheets-Sheet 8 Fig. I5

/oa 97 6 o t. svm i SOURCE l V 72 u I c, l r l l l /06 9a l se sglsl- E/04 /oo JA/V v/Vf l mi /0/ Inventors: Frank W Van ,Lu/Kfm Norman H.Wood,

Edward G. Kruszona.

The/'r- Attorney United States Patent O 3,250,060 ELECTROSTATICPRECIPITATOR Frank W. Van Luik, Jr., Norman H. Wood, and Edward G.Kruszona, Schenectady, N.Y., assignors to General Electric Company, acorporation of New York Filed Aug. 28, 1963, Ser. No. 305,075 11 Claims.(Cl. 55-114) The present invention relates to a new and improvedelectrostatic precipitator for removing minute aerosol particles from anair stream. More particularly, the invention relates to a new andimproved particle precipitator which is compact in design, and highlyefficient in operation.

Electrostatic precipitators have recently acquired signilicantly greaterimportance in industrial tacilities because of the problem of increasingair pollution by aerosol particles such as smoke, soot and other debri-scarried by the gaseous streams exhausted from such facilities.Previously available air cleaning devices for removing such debris havegenerally been too large in that they require extensive areas in whichto perform eiiiciently the operations of charging the aerosol to beremoved, i collecting the charged particles, and cleaning the co1-lected debris olf of the collecting members yand out of the path of theair stream.

A new and improved electrostatic precipitator which does not require alarge volume and which avoids the ineiiiciencies of previouslyY knownelectrostatic precipitators is disclosed in copending U.S. Patent No.3,149,936, issued September 22, 1964, Fllheodore A. Rich inventor,entitled, Electrostatic Precipitator, assigned to the General ElectricCompany. It is a primary object of the present invention to provide anew and improved electrostatic precipitator which incorporates the novelfea.- tures of the electrostatic precipitator disclosed in thelabove-identilied Rich Patent No. 3,149,936, and which is relativelycompact and highly eicient.

A further object of the present invention is the provision of `a new andimproved electrostatic precipitator which includes new and improvedapparatus for cleaning .the areas of precipitation, and for removing theprecipitated debris from the precipitator.

Briefly, in accordance with one form of the presen invention, an aerosolparticle precipitator is provided which comprises a source of ionsadapted to be positioned in a liuid stream containing undesired aerosolparticles to be removed. ,'Ilhe ion source preferably comprises a llamecharging source of the type described in the above-referred to copendingpatent of Theodore A. Rich. As described more completely therein, aflame of combustion creates both positive and negative ions, either ofwhich may be removed from the flame and mixed with the iluid stream byappropriate electric elds. Under the action of diiiusion and electricelds, ions from the source will adhere to aerosol particles entrained ina iiuid stream passing over the source. In thev present precipitator, abarile structure downstream from the source enhances the mixing of theions with the stream and increases the probability of collision.

Collection of the charged aerosol particles is performed by a set ofshaped collector plates maintained at an appropriate electric potentialdifferent from that of the source and shaped to provide fornon-turbulent ow of the air stream through the collection area. Thecollector plates, positioned vertically above the'source, are

A plurality of the cleaning chambers are positioned at horizontalintervals along the collector plates in the path of the iluid stream todivide the cleaning area into a plurality of sections. 'Iihe collectorplates are reciprocated so that the sections on which particles arecollected are presented to the scraping means for periodic cleaning. Alarge number of cleaning chambers may be used with short sectionstherebetween.

Other objects, features and many of the at-tendant advantages of thisinvention will be appreciated more readily as the same becomes betterunderstood by reference to the fol-lowing detailed description, whenconsidered in connection with the accompanying drawings, wherein likeparts in each of the several figures are identitied by the samereference character, and wherein:

iFIGURE 1 is a perspective view of a View and improved precipitatorconstructed in accordance with the present invention, and illustratesthe precipitator with its outer casing and some elements of internalstructure removed;

FIGURE 2 is a horizontal cross sectional view, partial along the unerv-rv of FIGURE 2;

FIGURE 5 is a vertical cross sectional view taken along the line V-V ofFIGURE 2;

`FIGURE 6 is a horizontal cross sectional View taken along the lineVI-VI of FIGURE 1;

FIGURE 7 is a vertical side view of the precipitator of FIGURE 1;

FIGURE 8 is a vertical cross sectional view taken along the lineVIII-VIII of FIGURE 6;-

FIGURE 9 is an enlarged illustration of a portion of FIGURE 6; l

FIGURE 10 is a vertical cross section-al view taken along the line X-Xof FIGURE 9;

FIGURE l1 is a vertical side view of the precipitattor of FIGURE 1illustrating the driving mechanism;

FIGURE 12 is -an illustration of a portion of the driving mechanism ofFIGURE l1;

FIGURE 13 is a vertical cross sectional view taken 'along the lineXIII-XIII of FIGURE 11;

FIGURE 14 which is on the same sheet with FIGURE 7 is a horizontal crosssectional vie-w taken along the line XIV-*XIV of FIGURE 8; and

-FIGURE l5 is a schematic circuit diagram of the circuit which controlsthe driving mechanism illustrated in FIGURE 11.

Overall preciptalor construction taining air stream through the bottomof the apparatus adapted to be reciprocated through narrow cleaning theapparatus, the debris will tall into hoppers at the bottom of eachchamber from which it may be removed.

illustrated into charging area 10 wherein an appropriate network offlameasustaining members is disposed. Electric potentials are appliedbetween the members and structure downstream from vthe members so thlations of a desired polarity are removed from the flame and mixed with theair stream to colli-de with the adhere to aerosol particles therein. Theair stream enters the precipitating area which may comprise any desirednumber of precipitating sections 1'1 separated by enclosed cleaningcharnybers 12. Electric elds in the precipitating sections 1-1 causedeposition of charged aerosol particles on appro-- priate collectorplates which are reciprocated through the vcleaning chambers 12 whereinthe accumulated debris is apparatus illustrated in FIGURE 1 and may bereleased into the atmosphere or used for any desired purposes.

Flame charging 'apparatus The apparatus of the present invention willbest be understood by considering successively each of the stepsperformed by the apparatus of FIGURE 1. With regard to the step ofcharging aerosol particles in a stream, the portion of FIGURE 1indicated generally by 10 is more clearly illustrated in FIGURES 2-5.The charging apparatus comprises walls 13 which enclose an array ofllame-sustaining members or llame tubes 14. The flame tubes 14 areadapted to sustain combustion flames 15 (best seen in FIGURE 3) thereonwhereby ions are produced in the high temperature zone "of the flame inthe manner disclosed in the above-identified Rich patent. Thisphenomenon has previously been described and deiined in the literature.

A combustible .gas for maintaining the flames 15 is introduced to liametubes 14 through a matrix of gas connecting pipes 16 and gas supplypipes 17, supplied through a gas coupling -member 18 and gas inlet pipe19 from an appropriate gas source (not shown). Oxygen is suppliedthrough a similarly arranged matrix of oxygen elements, namely, voxygenconnecting pipes 20 connected to the Viiame tubes 14 and oxygen supplypipes 21 supplied through an oxygen coupling member 22 and oxygen inletpipe 23 lfrom an appropriate oxygen source (not shown.) Gas and oxygenmay Ibe supplied through as many `such inle-t Ipipes as may be required`to main-tain the desired pressures ythroughout the system. The oxygenand gas supplies are, of course, kept distinct until mixing occurs inllame tubes 14. In order that the matrix of gas supply pipes 17 and theoxygen supply pipes 21 be arrayed in a planar arrangement, an elbowisprovided in one of the pipes at their intersections in the mannerillustrated in FIGURE 4 wherein gas supply pipe 17 is bent to pass overoxygen `supply pipe 21.

AThe entire system of connecting pipes 16, 20, supply -pipes 17, 21 andflame tubes 14 is composed of an yapprobers and ceramic insulators 31.An appropriate energizing potential -may be supplied to the flames, asillustrated in FIGURE -2, through a pair of solid high voltageconnectors 2'4 and 25 which are attached directly 'to the ysupply pipes17 and 21, respectively. Thus, the ame tubes 14 and the matrix of supplypipes may be connected to an appropriate potential, either positive ornegative, so that ions of the same polarity generated in the liames 15will be repelled, and will move toward a region of different potential.In accordance with the present invention, the different potential,preferably ground for reasons of safety, is applied to the collectingstructure in sections 11 (FIGURE 1) to attract charged aerosol particlesand remove them lfrom the air stream.

As shown in FIGURE 5, the flame tubes 14 each include appropriateinternal conduits 26 and 27, a swirl chamber 28 and a nozzle 29 wherebythe oxygen and gas are mixed. The mixture of oxygen and gas exitsthrough the nozzle 29 where it ignites and burns to provide iiames 15.The flames 15 are initially ignited by insertion of appropriate ignitonmeans through ports 32, shown in FIG- URE 1.

A significant improvement in the number of aerosol particles charged bycollision and adherence of ions can be made =by utilizing a bafestructure such as that shown in FIGURES 2 and 3 for mixing the ionsproduced by flames 15 with the air stream. This structure is maintainedat a potential of the same polarity as the collecting structure insections L1. The ibaiiie structure comprises an electrically conductivebaie plate 33 having an appropriate number of elongated apertures orslots formed therein which are oriented above each row -of liame tubes14. The plate must be thick to resist bending under the pressure of theair stream, but, it has been found that better mixing is obtained if theedges of the apertures above the flame tubes 14 are defined lbyrelatively thin members. Therefore, elongated thin strips 34 ofelectrically conductive material, are placed to overlie the edge of theapertures in plate 33 and are attached thereto. Cross members 35, alsocomprising thin strips of electrically conductive material, are attachedto members 34 to dene an aperture 36 above each flame tube 14. Verticalribs 37, extending the length of plate 33 to support its weight andprevent sagging, are mounted at each end to walls 13 by an angle iron38. The ribs 37, the angle irons 38, and the walls 13 are composed of anelectrically conductive material and are preferably maintained at thepotential of the collecting structure, namely ground.

The baliie 33 defines, with respect to each flame tube 14, a limitedarea through which the air stream must pass and further defines thelines of force of the electric iield established by the potentialdifference between iiame tubes 14 and plate 33. As a result, ionsemitted from the flames 15 will veither cross the air stream with a highprobability tof -collision with aero-sol particles, or will travelparallel to the air stream for an extended distance thereby increasingthe probability of mixing and colliding with yaerosol particles ybymeans of diffusion. In general, the effect of the baffle struc-ture isto greatly increase the number of aerosol particles which are charged byions from the llames.

' Precl'ptating section The net result of the apparatus contained inarea 10 'is the charging `of a very high percentage of the aerosolparticles entrained in the gaseous stream passing through the apparatuswith ions produced by llames 15. The next step to be performed by theapparatus is that of precipitating the charged particles out of thegaseous stream. This is accomplished'in the precipitating `sections 11,disposed above charging area llt), which will now tbe described inconnection with FIGURES 1, 6 and 7. The precipitating sections 11, aside View of which is shown in FIG- URE 6, may be as wide or as narrowas desired, although it is preferable that vall ysections 'be of equalwidth. There may be as many sections as desired, since several sectionswill be more eiiicient and the precipitating area may be as wide as lisrequired by the application. Each section 11 includes a series of iixedelectrode plates 40 alternated with movable collector plates 41, thecollector plates extending through all sections and being of a width onesection wider than the total width of all the precipitating sections 11as will be more completely described below. The electrode plates 40 areattached by means of angle clips 42 to a frame 43 and the frame 43 ismounted on an appropriate number of standoff insulators 44. Theinsulators 44 rest von precipitator frame members 45 (best seen inFIGURE 7) which support the various elements of the apparatus. Theelectrode plates 40 are composed of an electrically conductive materialsuch as steel, and angle clips 42 and frame 43 are also of electricallyconductive material. By this means, an electric potential applied toframe 43 by means such as conductor 46, introduced through ceramicinsulator 47 and lead 48 will be distributed to all of the electrodeplates 40.

In order to decrease turbulence adjacent the electrode plates, they maybe fabricated to have a cross section which is a maximum at the top ofthe section 11'and which tapers to a minimum at the bottom. The taperneed only be slight, for example, the thickness may vary fromonesixteenth inch at the bottom to three-sixteenths inch at the top overa five-foot length. However, it has been Afound that shaping theelectrode plates in this manner maintains the gaseous medium flowingpast the plates in a non-turbulent ow condition, Iand greatly increasesthe etliciency ofthe percipitator as described more fully in the abovereferred to Rich Patent No. 3,149,936. To avoid 'the possibility ofsparkover, the bottom edge of electrode plates 40 may be rounded,thereby .avoiding a sharp point from which a spark might start.

The collector plates 41 which extend across the precipitating sections11 are composed of an electrically conductive material and are connectedelectrically to the Isame potential, preferably ground, as the batilestructure. Ions which pass through the baile structure will move alongelectrostatic lines of force which are nearly par-allel to the flowlinesof the air stream and which terminate on the collector plates 41. Due tothe distance over which the lines of force and the owlines are nearlyparallel, ions and aerosol particles will mix by diffusion and nearlyall of the aerosol particles which escape charging Vnear the -baiiiestructure will be charged by collision and adherence of ions travelingto the collector plates. An electric potenti-al is applied to theelectrode plates 40 and the electric iield established between'collectorpl-ates 41 and efectrode plates 40 will result in the precipitation oncollecto-r plates 41 of charged aerosol yparticles passing therebetween.Although the values of potentials can be varied, it is necessary thatthe electrode plates 40 be of the same polarity as the flame tubes 14,and that both be of opposite polarity from the collector plates 41 sothat ions emitted from the flames will be rcpelled by the electrodeplates and attracted to the collector plates. The baiiie structureshould also be of a polarity to attract ions emitted from the llames,but it should not me more attractive than the collector plates. Asimilar precipitation occurs in each of the precipitating lsections 11and therefore, due to the high eiciency of the apparatus described, theair stream leaving the top of the precipitator will be' almostcompletely free of the aerosol particules pre, viously entrained.

Cleaning section The apparatus in cleaning chambers 12 for removingaccumulated debris from collector plates 41 will now be described. Thecollector plates 41 are reciprocally driven across the air-column sothat each section of the collector plates which is exposed toprecipitation of particles is moved through one cleaning chamber 12. Theapparatus in cleaning chambers 12 will be best understood by aconsideration of FIGURES 6-10.

Cleaning chambers 12 include a plurality of rollers 50 mounted on eachside of the chamber as shown in FIG- URE 6. The rollers 50 deiine thecleaning chambers Iand are designed to roll at the same surface velocityas the collector .plates 41 so that there is no scraping action therebypreventing re-entrainment `of debris from collector plates 41 back intothe air stream being filtered. Additiona'lly, the rollers 50 serve toseal off the cleaning chambers from the precipitating sections 'therebyfurther preventing any re-entrainment of the debris cleaned oit in thecleaning chambers back into the air stream. For this purpose, therollers 50 are rotatably supported along each side of the chambers 12,and the collector plates 41 pass between them, as illustrated in FIGS. 6and 9. The roller shafts 51 are journalled in appropriate bearings 52 atthe base of the chamber, and at the top of the chamber, and the rollershafts 51 extend through apertures 53 in a bar 54 that is bolted toframe member 45. The apertures in the Ibar 54 are slightly larger thanthe shafts as illustrated in FIGURES 8 and 9, andV a collar 55 mountedat the top of each roller rides against the surface of two of thecollector plates 41. Each segment of the cleaning chambers 12 is delinedby one pair of the rollers 5 0 and the respective rollersl of the pairsare disposed in rows which extend across the full length of theprecipitating region. The e-nd rollers in each row are interconnected byangle clips 56, rods 57, turnbuckles 58, rods 59, and springs 60. Thesprings 60 are then connected to the axle of the center roller by meansof strip 61 and bolt 62. By proper adjustment of thel turnbuckles 58,the collars 55 are pressed iirmly against the surface of collectorplates 41, thereby restricting the space between collector plates 41 androllers 50 to the thickness of collars 55 which may be approximately142. This allows collected debris to enter 'the cleaning chamber onplates 41.

Cover plates 63 are disposed-over the tops of cleaning chambers 12 and asquare support member or rod 64 (best shown in FIGURE 9) dependstherefrom into each cleaning chamber segment between the defining pairof rollers and each pair of plates. A scraper 65 is mounted on each sideof the square rod 64 by suitable fastening means such as screws 66. Eachscraper 65 comprises a strip of metal, for example, phosphor bronze,which extends parallel to the axis of the rollers and which has 'beenbent into the configuration shown in FIGURE 9. The scrapers :areattached along one edge to support member 64, and are formed to providea plurality of sets of horizontal fingers 67 which are arranged side by-side Ialong the length ofthe roller as illustrated in FIGURE 10. Thescrapers are so sized that the tips of the fingers 67 are perpendicularto and engage the 'surfaces of the adjacent collector plates 41 and thesurfaces of the rollers 50. The bend in scrapers 65 is adjusted so thatthe lingers 67 engage the various surfaces with sufficient pressure toremove any accumulated material precipitated on collector plates 41 orcollected by rollers 50 without damaging the surfaces.

Under the force of gravity, debris removed by fingers 67 from collectorplates 41 and rollers 50, will fall into the enclosed hoppers 68 at thebase of each cleaning chamber as illustrated in FIGURE 7. The debris maythen readily be removed from hoppers 68 by any appropriate means. Apreferred removal means is a Vacuum system since this creates a pressuredifferential across the openings between chambers 12 and sections 11 andreduces the possibility of re-entrainment of particles.

Reciprocating mechanism.y

The mechanism by which the collector plates 41 are reciprocated will nowbe described. This may best be understood by a consideration of FIGURES1, 6 and 1l- 14. As previously stated, and 'as shown in FIGURE l, thecollector plates 41 extend throughout the width of the totalprecipitating area, including `all precipitatingsections 11 and cleaningchambers 12. Additionally, each collector plate 41 extends beyond thisregion by a distance equal to the width of the widest precipitatingsection. FIGURE 1 illustrates the preferred embodiment wherein allsections 11 are equal in width and the collector plates are onev sectionwider than the air stream. i

Alternate collector plates 41 are positioned so that thev additionalwidth extends into areas at opposite sides of the precipitating area.The purpose of this additional rwidth is to allow the plates to bereciprocated through the precipitating area while at the same timemaintaining a given surface area in each section for precipitation.Thus, the plates whichare initially in the area indicated at 70 inFIGURE 1 and extend to the beginning of area 71 may be moved adistance-equal to the width of the widest section to the right in FIGURE1, and all surfaces will have passed through one cleaning chamber 12,but a portion of the collector plate having a given collecting surfacearea will always be in collecting position in all of the precipitatingsections 11. Similarly, the alternate collector plates 41 whichinitially extend into area 71 and terminate adjacent area 70 may bemoved to the left in FIGUREl so that all sections of the plates passthrough one cleaning chamber 12, and a portion of the collector platehaving a given collecting surface area will always be in collectingposition in all of the sections 11.

The driving mechanism to accomplish the above result is comprised by amotor 72 shown in FIGURES l and 11, andra system of drive chains andsprockets associated therewith. Motor 72 is mounted on frame members 45,and'drives shaft 73 through drive chains 74 and sprockets 75. Shaft 73is supported on frame members 45 by journals 77, and has a plurality ofsprockets 77 mounted along its length, the total number of sprocketsbeing equal to the number of plates 41. A drive chain 78 is connected toeach plate 41 by means of a connector 79, and each extends respectivelyover an associated sprocket 77. In the case of one of the alternatecollector plates in the set which initially extend into area 70 forexample, the drive chain 78 extends over the top of the respectiveassociated sprocket 77, under an idler sprocket 80 for reversingdirection of the chain, and up to one side of a pipe 81. The sprockets80 are mounted on shaft 82 which is journalled in bearings 83 likewisesecured to the lower frame members 45. In the case of the remainingcollector plates 41, that is, those which initially extend into area 71,the respective drive chains 78 extend under the respective sprockets 77,over idler pulleys 84 and downwardly to a connection to the remainingside of the pipe 81. The idler pulleys 84 are supported on a shaft 85journalled in bearings 86 secured to the upper frame members 45. Theconnection of the respective drive chains 78 to the pipe 81 isillustrated in FIGURE 12, the connection of all the chains beingidentical except for orientation. Each chain is connected to a threadedrod 87 which extends through the pipe 81 and a shock absorbing assembly,comprising spring 88, is supported over the end of the rod 87 extendingthrough pipe 81 by washers 89 and nut 90. By reason of thisconstruction, the spring 88 will cushion initial movement and stoppingof the plates 41 by their respective drive chains 78 In order to providea balanced load on the drive motor 72, alternate pairs of collectorplates 41 are attached at their opposite ends by means of connectors 91to drive chains 92 so that the set of plates which is being moved i bymotor 72 into area '70 will pull the alternate set of plates into area71. The drive chains 92 are connected over reversing idler pulleys 93which are supported by I-beam 94 attached to frame members 45. The idlerpulleys 93 are set at angle with respect to the collector members 41 asillustrated in FIGURE 13 to facilitate interconnection between theadjacent plate 41.

The collector plates 41 are supported on blocks lof bearing material,illustrated at 95 in FIGURE 14, for example' a phenolic asbestoscompound such as that designated R-860, manufactured and sold by theRaybestos Manhattan Company. The material selected should be longwearing and have a low coefficient of friction so that the plates slideeasily over it. The bearing material is mounted in the frame of theapparatus adjacent the supports 48 for roller shafts 47.

During operation of the precipitator as the motor drives sprockets 75,the pipes 81 are reciprocated, ensuring uniform motion of all collectorplates 41. As a result of reciprocation of pipes 81, half of the plates41 are moved from a position of extension into area 71 into a positionof extension into area 70 by the drive chains 78 while the other half ofplates are moved oppositely by drive chains 92. Alternately, the reverserelation is brought about by continued reciprocation of pipes 81 by thedrive motor 72. This reciprocation of pipes 81 may be either periodic orcontinuous depending upon the necessity for cleaning plates 41.Connecting each collector plate 41 to a drive sprocket 77 and, through achain 92, to the adjacent collector plate prevents any one collectorplate from being critical to the movement of the remainder, since it isnot desirable that one broken chain cause all of the plates to stop. Inthe system as decribed above,-

a maximum of two plates will stop reciprocating if one chain breaks.

FIGURE l illustrates the circuit used to control motor 72 whichreciprocates the collector plates 41. The motor 72 is connected to apower source 96 through reversing switch 97 which is controlled by thecoils 98 and 99. The coilsare energized from an appropriate source ofcontrol voltage through switches 100 and 101, both of which .arespring-biased open. Due to the parallel connection, closure of either ofswitches 100 or 101 will cause switch 97 to be rotated 90, thusreversing the connection of motor 72 across its power source andreversing its direction of rotation. Switches 100 and 101, also shown inFIGURE 11, are rotary switches actuated by plates 41 through ahorizontal bar 102 and arm 103. Arrival of either set of collectorplates, or of any one plate at the end of its path will actuate one ofthe swiches 100 or 101 to reverse motor 72.

To prevent burnout in 'case of the failure of the switching mechanismillustrated above, overrun protection switches 104 and 105, shown inFIGURE 15, may be provided to energize coil 106 and open switches 107and 108, thereby stopping motor 72. In the arrangement shown, overrunmust occur on both sides of the precipitator before the motor will beshut oil.

Overall operation In operation, it will be understood from the precedingdescription that upon appropriate fuel being supplied to llame tubes 14and llames 15, and after being initially ignited, the llames will besustained thereby. A high voltage is applied to the llame tube 14, forexample through the network of fuel supply pipes, and the housing of theprecipitator is connected to a different potential, preferably ground.Through the medium of the mechanical connections of electricallyconductive materials, baille plate 33 and the associated baillestructure and collector plates 41 will be at the same potential as thehousing. The electrode plates 40 are connected through conductor 46 to apotential of the same polarity as the llame tubes 14. One example ofsuitable working potentials for the arrangement is 20,000 voltsconsisting of an equality of potential applied to the electrode plates40, and 5,000 volts of the same polarity applied to the llame tubes 14,although it should be understood that these values are merelyrepresentative, and other values will work equally well.

A iluid stream, for example air, bearing aerosol particules is directedupwardly into charging area 10 wherein ions emitted from flames 15 byvirtue of the established electric 'ields will collide with and adhereto the aerosol particles. The 'baille structure assures nearly completecharging of the entrained aerosol particles. The air stream then entersthe collecting area precipitating ysections 11 wherein the electricfields set up by the respective potentials on electrode plates 40 andcollector plates 41 will cause the charged aerosol particles to becollected on the collector plates 41. The clean iluid stream will thenexhaust through the top of the precipitator. Concurrently with theabove-described collecting action, the collector plates 41 are slowlyand continuouslyvreciprocated through cleaning areas 12 by motor 72A andthe above-described driving connections, the cleaning chambers lbeingdeilned by the rollers 50. Within the cleaning chambers, the lingers 67vof Scrapers 65 rub against the collector plates 41 and rollers 50 toremove precipitated particles. The particles, due to the force ofgravity, fall into hoppers 68 from which accumulated debris may beremoved by vacuum means or in any appropriate manner.

An important feature of the present invention lies in the small cleaningchambers described above. The narrow cleaning chambers 12 and thescraping means contained therein are highly eillcient in removingprecipitated particles from the collector plates. Since an extendedcleaning area is not required, cleaning chambers 12 may be disposed atdesired intervals across the air column, and ythe successiveprecipitating sections may be relatively narrow. Thus, the plates needonly be reciprocated through a small distance to achieve completecleaning. This allows for compactness of design without impairment ofthe collector plate cleaning operation. Additionally, the design allowsthe rollers 50 to electively 9 seal off thecleaning chambers 12 from theprecipitatin sections thereby avoiding any re-entrainment of the debrisback into the air stream.

Two significant advantages result from the above compactness of designfeature. First, the areas 70 and 71 into which the collector platesextend during alternate cycles need only equal the width of one sectionrather than the width of the entire precipitating area. For example, iften precipitating sections one foot in width were provided, the overallapparatus would only have to be about twelve feet wide to accommodatethe collector plates in areas 70 and 71 instead of 30 feet as isrequired by previous electrostatic precipitators. The total width,rather than being three times Ithe width of the precipitating area, isonly two sections greater than the precipitating area. This results in asavings in thecost of materials-for constructing the device as well asin economy of space at the eventual location of the precipitato-r.

The second advantage resulting from the close spacing of narrow cleaningchambers 12 is the higher frequency with which the areas of thecollector plates are cleaned for a given plate speed. Due to the sizeand weight of the collector plates, it is more feasible and practical tomove them at a relatively low rate of speed. In priorprecipitators,-where any given area passed through the entireprecipitating column before being cleaned, a relatively high rate ofspeed had to be maintained or else a buildup of precipiated particlesoccurred which decreased the efliciency of the precipitator. In the caseof the present apparatus, the plates may be moved at a low rate of speedand each area will still be frequently cleaned due to the short distancebetween chambers 12.

Another important feature of the above described apparatus lies in theuse of sc rapers 65 divided'into iingers 67. Since the fingers formed anearly continuous removal edge, the entire surface of the collectorplates will be scraped and cleaned. The light spring .tensioning of thefingers 67, provided by the curved shape of the scraper 65 and of theinitial portion of the fingers 67, ensures suflicient pressure againstthe collector plates to remove all precipitated particles. The fingers67 are used rather than a continuous scraping edge to maintain contactwhich might be lost if an area of a continuous edge became bent. Such abend could remove an extended portion of the scraping means from contactwhereas the fingers 67 would be individually bent and would not causeextended loss of scraping contact.

Another significant feature of the invention is the ver. ticalarrangement of the collector electrode plates 40, 41 over the air streamto be cleaned thereby reducing the pressure drop through the'system andallowing the collected particles to be removed more efficiently.

From the foregoing description, it can be appreciated that the presentinvention provides a new and improved electrostatic precipitator whichis smaller and more highly efficient than previously knownpreeipitators. It i's, therefore, to be understood that othermodifications and variations of the invention are possible in the lightof the above teachings. Hence, Vchanges may be made in the particularembodiment of the invention described which are within the full intendedscope of the invention as dened by the appended claims.

What we claim as new and desire to secure by Letters Patent of theUnited States is:

1. An aerosol particle precipitator comprising:

(a) a source of electrically charged particles for imparting an electriccharge to aerosol particles entrained in a fluid stream; y

(b) collecting means positioned downstream from said source andcomprising a plurality of spaced generally parallel movable collectorplates maintained at a predetermined electric potential different fromthat of said source;

(c) a plurality of cleaning chambers extending transversely to andintermediate adjacent ones of said Cil , 10 movable collector plates andcontaining means for removing precipitated particles from each saidadjacent collector plates; (d) roller means positioned on each side ofeach cleaning chamber and engaging the collector plates on each sidethereof for sealing off the cleaning chambers toA prevent reentrainmentof particles cleanedfrom the collecting plates back into the lluidstream being cleaned, said cleaning chambers and associated roller meansbeing positioned at intervals along said collector plates and dividingsaid collector plates into a plurality of sections whereby saidcollector plates need be moved only a distance equal to the spacingbetween successive cleaning chambers to effect complete cleaning of saidcollector plates; and

(e) means for moving said collector plates.

`2. An aerosol particle precipitator as recited .in claim 1, whereinsaid source of electrically charged particles comprises:

(a) an array of flame-sustaining members;

(b) a network of supply pipes for providing fuel to saidflame-sustaining members, said supply pipes and said members beingmaintained at a predetermined electric potential; and

.(c) |baliie means spaced from said array of ame-sustaining members andmaintained at an electric potential different from the electricpotential of said ame sustaining members.

3. An aerosol particle precipitator as recited in claim 1, wherein saidcollecting means further comprises:

(a) a plurality of electrode plates interleaved with and substantiallyparallel to said collector plates;

(b) said alternate electrode plates being slightly tapered outwardlytoward the downstream side 4to provide non-turbulent flow of air throughthe collector plates; and

v(c) said electrode plates being maintained at an electric potentialofthe same polarity as that of said source.

4. An aerosol particle precipitator comprising:

(a) a source of electrically charged particles comprising aflame-sustaining member positioned in a fluid stream and maintained at apredetermined electric potential;

(b) collecting means positioned downstream from said source andcomprising a plurality of spaced generally parallel movable verticalcollector plates maintained at a predetermined electric potentialdifferent from that of said source;

(c) a plurality of vertically disposed cleaning chambers extending thefull width of and intermediate adjacent ones of said movable collectorplates and containing scraping means for removing precipitated particlesfrom each said adjacent collector plates;

(d) roller means positioned on each side of each cleaning chamber andengaging the collector plates on each side thereof for sealing olf thecleaning chambers to prevent reentrainment of particles cleaned fromthe. collecting plates back into the fluid stream being cleaned, saidclean-ing chambers and associated roller means being positioned atintervals along said collector plates and dividing said collector platesinto a plurality of sections whereby said plates need Ibe moved only adistance equal to the spacing between successive cleaning chambers toeffect complete cleaning of said collector plates; and

(e) means for horizontally moving said collector plates.

5. An aerosol particle precipitator as recited in claim 4 wherein ahopper is positioned at the bottom of each of said cleaning chambers forcollect-ing particles removed from said collector plates.

6. An aerosol particle precipitator as recited in claim 4 wherein eachof said scraping means comprises an elongated assembly having at leasttwo rows of individual fingers extending therefrom -in oppositedirections, each 1 1 I of said assemblies being positioned betweenadjacent collector plates, said fingers engaging an elemental width onsaid collector plates with each row of fingers providing a continuousscraping edge extending the full distance along one dimension of thecollector plates to remove precipitated particles therefrom.

7. An aerosol particle precipitator as recited in claim 4 wherein eachof said scraping means comprises an elongated support member and atleast two elongated strips, each of said support members beingpositioned between adjacent collector plates, each of said strips beingattached to said support member along one edge and being cuttransversely along the opposite edge to provide a plurality ofindividual extended lingers in a continuous row, each of said fingersbeing bent in the form of a U-shaped tension spring to provide tensionwhich causes each of said lingers individually to engage a discreteelemental width of said collector plates.

8. The aerosol particle precipitator as recited in cla-im 4 wherein eachof the scraping means lcomprises four rows of individual extendedfingers mounted adjacent one another to provide a continuous scrapingedge extending the full distance along one dimension of the collectorplates and associated roller means of each cleaning chamber, thescraping means thus comprised being mounted in each of said cleaningchambers for engaging the lcollector plates and roller means to removeprecipitated particles therefrom. l

9. In an aerosol particle precipitator as set forth in4 claim 4 whereinsaid scraping means comprises an elongated assembly positioned betweensuccessive collector plates and their associated roller means in eachcleaning station, said assembly having a central support member and fourelongated strips, each of said strips being attached to-said supportmember along one edge and being cut at the opposite edge to provide aplurality of fingers arrayed in a continuous row with each of saidlingers being bent in the form of a U-shaped tension spring to providetension which causes each of .said lingers individually to engage adiscrete elemental width of the collector plates and roller means forremoving precipitated particles therefrom.

10. The aerosol particle precipitator set forth in claim 4 wherein said-collecting vmeans further comprises:

(a) a plurality of vertical electrode plates interleaved with and spacedsubstantially parallel to said vert-ical collector plates, andmaintained at an electric potential having the same polarity as saidsource; and

(b) said alternate vertical electrode plates being slightly taperedoutwardly towards the downstream end 12 to provide non-turbulent flow ofair through the collector plates.

11. The aerosol particle precipitator set forth in claim 4 wherein saidsource of electrically charged particles comprises:

(a) an array of llame-sustaining members;

(b) a network of supply pipes for providing fuel to saidflame-sustaining members, said supply pipes and said flame-sustainingmembers being maintained at a predetermined electric potential; and

(c) a 'baie means spaced from said array of llamesustaining members andmaintained at an electric potential different from the electricpotential of said llame-sustaining members; and wherein said collectingmeans further comprises;

(d) a plurality of vertical electrode plates interleaved with and spacedsubstantially parallel to said vertical collector plates; and maintainedat an electric potential having the same polarity as said source; and

(e) said alternate vertical electrode plates being slightly taperedoutwardly towards the downstream end to provide non-turbulent flow ofair through the collector plates; and wherein each of said scrapingmeans comprises:

(f) an elongated assembly having at least two rows of individual lingersextending therefrom -in opposite directions, each of said assembliesbeing positioned between adjacent collector plates with said lingersengaging an elemental width on said collector plates with each row offingers provid-ing a continuous scraping edge extending the fulldistance along one dimension of the collector plates to removeprecipitated A particles therefrom.

References Cited by the Examiner UNITED STATES PATENTS 986,118 3/1911Alexander 55-290 X 3,149,936 9/1964 Rich 55-114 FOREIGN PATENTS 435,5743/1927 Germany.

359,686 3/ 1962 Switzerland.

OTHER REFERENCES German printed application No. 1,078,096, March 1960.

ROBERT F. BURNETT, Primary Examiner.

1. AN AEROSOLS PARTICLES PRECIPITATOR COMPRISING: (A) A SOURCE OF ELECTRICALLY CHARGED PARTICLES FOR IMPARTING AN ELECTRIC CHARGE TO AEROSOL PARTICLES ENTRAINED IN A FLUID STREAM; (B) COLLECTING MEANS POSITIONED DOWNSTREAM FROM SAID SOURCE AND COMPRISING A PLURALITY OF SPACED GENERALLY PARALLEL MOVABLE COLLECTOR PLATES MAINTAINED AT A PREDETERMINED ELECTRIC POTENTIAL DIFFERENT FROM THAT OF SAID SOURCE; (C) A PLURALITY OF CLEANING CHAMBERS EXTENDING TRANSVERSELY TO AND INTERMEDIATE ADJACENT ONES OF SAID MOVABLE COLLECTOR PLATES AND CONTAINING MEANS FOR REMOVING PRECIPITATED PARTICLES FROM EACH SAID ADJACENT COLLECTOR PLATES; (D) ROLLER MEANS POSITIONED ON EACH SIDE OF EACH CLEANING CHAMBER AND ENGAGING THE COLLECTOR PLATES ON EACH SIDE THEREOF FOR SEALING OFF THE CLEANING CHAMBERS TO PREVENT REENTRAINMENT OF PARTICLES CLEANED FROM THE COLLECTING PLATES BACK INTO THE FLUID STREAM BEING CLEANED, SAID CLEANING CHAMBERS AND ASSOCIATED ROLLER MEANS BEING POSITIONED AT INTERVALS ALONG SAID COLLECTOR PLATES AND DIVIDING SAID COLLECTOR PLATES INTO A PLURALITY OF SECTIONS WHEREBY SAID COLLECTOR PLATES NEED BE MOVED ONLY A DISTANCE EQUAL TO THE SPACING BETWEEN SUCCESSIVE CLEANING CHAMBERS TO EFFECT COMPLETE CLEANING OF SAID COLLECTOR PLATES; AND (E) MEANS FOR MOVING SAID COLLECTOR PLATES. 